Process for isolating 170 isotope from water and process for concentrating 170 isotope using the same

ABSTRACT

A process for isolating  17 O from water and a process for concentrating  17 O by using the same are provided. The process for isolating  17 O from water includes: mixing  17 O-containing water with formaldehyde to prepare an aqueous formaldehyde solution; heating the aqueous formaldehyde solution to generate a vapor mixture containing water vapor and formaldehyde vapor; and obtaining  17 O-depleted water, residual formaldehyde, and a gas mixture containing hydrogen and  17 O-enriched carbon monoxide, through photodissociating the vapor mixture. An  17 O-enriched water production process includes: an operation of adding hydrogen to the gas mixture to induce a catalytic methanation reaction to synthesize methane (CH 4 ) and  17 O-enriched water (H 2   17 O) through methanation, the operation being carried out following the process for isolating  17 O from water.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to Korean PatentApplication No. 10-2018-0141478 filed on Nov. 16, 2018 and Korean PatentApplication No. 10-2019-0003990 filed on Jan. 11, 2019 with the KoreanIntellectual Property Office, the disclosure of which is incorporatedherein by reference in its entirety.

BACKGROUND 1. Field

The present disclosure relates to a process for isolating ¹⁷O from waterand a process for concentrating ¹⁷O using the same, and morespecifically, to a process for removing ¹⁷O from heavy water or lightwater by using water as a starting material, and to a process forisolating ¹⁷O from water and concentrating the same.

2. Description of Related Art

Oxygen exists as three stable isotopes in the natural state, ¹⁶O, withthe natural abundance of 99.758%, ¹⁷O with the natural abundance of0.037%, and ¹⁸O with the natural abundance of 0.204%. Here, ¹⁷O-enrichedwater enriched with ¹⁷O having a nuclear spin of 5/2 to 10% or higherhas been used as the raw material for nuclear magnetic resonance (NMR)compounds and as a contrast agent for magnetic resonance imaging (MRI).Such ¹⁷0-enriched waters are quite costly, in that 20% ¹⁷O-enrichedwater costs about 600 dollars per gram, while 90% ¹⁷O -enriched watercosts about 3,500 dollars per gram.

The materials used as moderators in nuclear reactors, namely, graphite,light water (¹H₂O), and heavy water (D₂O), contain stable isotopesincluding ¹⁷O, ¹⁴N, ¹³C, and the like, and these isotopes react withneutrons to form a radioactive isotope, ¹⁴C. ¹⁴C has a half-life of5,730 years and is an organic radionuclide harmful to the human body,and therefore, is a main radionuclide of interest that is strictlyregulated in nuclear power plants and radioactive waste treatment sites.Countries in Europe, as well as Canada, the US, and Japan have struggledwith the disposal of irradiated graphite produced from gas-cooledreactors and ¹⁴C waste materials produced from heavy water in heavywater reactors. Since the amount of undisposed ¹⁴C currently storedworld-wide has reached 500,000 Ci, exceeding the total limit permittedfor the entirety of nuclear waste disposal sites, and as relevantregulations have become increasingly more strict, a fundamentalreduction of the amount of carbon-14 generated in nuclear reactors is anurgent and pressing matter.

Heavy water (D₂O) used as a coolant and moderator in heavy water nuclearreactors contains 0.037-0.059% of ¹⁷O isotope. The amount of ¹⁴Cgenerated from a heavy water nuclear reactor of 1 GWe/yr, which usesabout 600 tons of heavy water, has reached 700 Ci per year, wherein 95%or more of this amount is being formed from ¹⁷O contained in the heavywater. Accordingly, reducing the amount of ¹⁷O contained in the heavywater to 1/10 or less may result in reducing the amount of ¹⁴C generatedfrom the heavy water nuclear reactors by 90% or more.

Distillation is known as a commercial technique for isolating oxygenisotopes, such as ¹⁸O and ¹⁷O. Water distillation, a technique whichseparates water at 320 K, has isotope selectivity for ¹⁸O of about1.007. Oxygen cryogenic distillation, a technique which isolates oxygenisotopes by distilling liquid oxygen at 90 K, has isotope selectivityfor ¹⁸0 isotopes of about 1.102. Therefore, it is deemed that reducingthe isotopic abundance of ¹⁷O to 0.037% or less, in a cost-effectivemanner, cannot be achieved by currently available techniques. In theabove context, U.S. Pat. No. 8,337,802 B2 has proposed a method thatisolates ¹⁷O isotopes through photodissociation of ozone at 160 K byusing a near-infrared laser with a wavelength of 998 nm; however, thismethod has relatively low selectivity for ¹⁷O of about 2.2, and thus mayhave limited potential as a commercially useful technique.

Accordingly, processes capable of isolating ¹⁷O isotope from water withhigh selectivity and concentrating the same may be expected to find awide range of useful applications in related fields.

SUMMARY

An aspect of the present disclosure may provide a process for isolating¹⁷O from water.

Another aspect of the present disclosure may provide a process forconcentrating ¹⁷O using the process for isolating ¹⁷O from water of thepresent disclosure.

According to an aspect of the present disclosure, a process forisolating ¹⁷O from water may include: preparing an aqueous formaldehydesolution by mixing ¹⁷O-containing water with formaldehyde; preparing avapor mixture containing water vapor and formaldehyde vapor by heatingthe aqueous formaldehyde solution; and photodissociating the vapormixture to obtain a gas mixture containing hydrogen and ¹⁷O -enrichedcarbon monoxide, ¹⁷O-depleted water, and residual formaldehyde.

According to another aspect of the present disclosure, a process forproducing ¹⁷O-enriched water may include: an operation of obtaining agas mixture containing hydrogen and ¹⁷O -enriched carbon monoxide, ¹⁷O-depleted water, and residual formaldehyde, from ¹⁷O -containing waterby the process for isolating ¹⁷O from water of the present disclosure;and a catalytic methanation operation of adding hydrogen to the gasmixture to induce a catalytic methanation reaction to synthesize methane(CH₄) and ¹⁷O -enriched water (H₂ ¹⁷O ) through methanation.

BRIEF DESCRIPTION OF DRAWINGS

The above and other aspects, features, and advantages of the presentdisclosure will be more clearly understood from the following detaileddescription, taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 schematically shows a process for isolating ¹⁷O from water and a¹⁷O -enriched water production process according to the presentdisclosure (501: aqueous formaldehyde solution (373 K), 502:formaldehyde photodissociation device (373 K), 503: formaldehyde andwater trap device (100 K), 504: methanation device, 505: ¹⁷O -enrichedwater trap device (243 K), and 506: recirculating the ¹⁷O -enrichedwater for further concentration);

FIG. 2 shows the photodissociation spectrum of formaldehyde around28,375 cm⁻¹ (101: the photodissociation spectrum of formaldehydecontaining ¹⁷O in natural isotopic abundance of 0.037%, and 102: thephotodissociation spectrum of formaldehyde enriched with ¹⁷O to 3.8%);

FIG. 3 shows the photodissociation spectrum of formaldehyde around28,397 cm⁻¹ (201: the photodissociation spectrum of formaldehydecontaining ¹⁷O in natural isotopic abundance of 0.037%, and 202: thephotodissociation spectrum of formaldehyde enriched with ¹⁷O to 3.8%);and

FIG. 4 shows the relationship between the ¹⁷O concentration (abundance)of a photodissociated product (CO) and the ¹⁷O concentration (abundance)in tail water, in a ¹⁷O isolation process with selectivity for ¹⁷O of400 (301: heavy water enriched with ¹⁷O to 0.059%, and 302: light waterenriched with ¹⁷O to 0.037%).

DETAILED DESCRIPTION

Hereinafter, embodiments of the present disclosure will be described asfollows with reference to the attached drawings. The present disclosuremay, however, be exemplified in many different forms and should not beconstrued as being limited to the specific embodiments set forth herein.

As will be described in detail hereinbelow, a process for isolating anoxygen isotope from water of the present disclosure, due to havingexcellent isotope selectivity for ¹⁷O, may focus energy solely on ¹⁷O toisolate the same, thus achieving extremely high energy efficiency, andmay enable large-batch production in relatively small-scale facilities.

In detail, a process for isolating an oxygen isotope from water of thepresent disclosure may include: preparing an aqueous formaldehydesolution by mixing water containing an oxygen isotope with formaldehyde;preparing a vapor mixture containing water vapor and formaldehyde vaporby heating the aqueous formaldehyde solution; and photodissociating thevapor mixture to obtain a gas mixture containing hydrogen and carbonmonoxide enriched with the oxygen isotope, water depleted of the oxygenisotope, and residual formaldehyde.

In particular, the oxygen isotope that can be isolated in the presentdisclosure may be ¹⁷O.

In the preparing an aqueous formaldehyde solution by mixing watercontaining an oxygen isotope with formaldehyde, the formaldehyde may bemixed in water preferably in a molar ratio in the range of 0.01 to 0.3with respect to water, more preferably in the range of 0.01 to 0.25, andfor example, the formaldehyde may be mixed in water in a molar ratio inthe range of 0.05 to 0.2 with respect to water. Mixing with theformaldehyde in an amount less than the lower limit of the above rangesmay give rise to insufficient oxygen-isotope exchange reactions, causingan undesirable decrease in productivity, whereas mixing with theformaldehyde in an amount exceeding the upper limit of the above rangesmay give rise to an undesirable formation of formaldehyde polymers.

After preparing the aqueous formaldehyde solution, preparing a vapormixture containing water vapor and formaldehyde vapor heating theaqueous formaldehyde solution may be carried out, wherein the heatingmay be carried out at a temperature in the range of 320-400 K,preferably in the range of 350-380 K.

The vapor mixture, once obtained, may be photodissociated to produce agas mixture containing hydrogen and carbon monoxide enriched with theoxygen isotope, water depleted of the oxygen isotope, and residualformaldehyde.

In particular, the photodissociating the vapor mixture may be preferablycarried out under a pressure in the range of 1-15 Torr, and for example,may be carried out under a pressure in the range of 5-10 Torr. When thephotodissociating the vapor mixture is carried out under a pressure lessthan the above ranges, it may cause an undesirable decrease inproductivity; however, when the photodissociating the vapor mixture iscarried out under a pressure greater than the above ranges,photodissociation quantum yield may undesirably decrease to 85% or less.

In particular, according to the present disclosure, an optic fiber lasermay be used to irradiate a laser of a particular wavenumber. Inparticular, the wavenumber of a photodissociating laser for thephotodissociating the vapor mixture may be in the range of 28,370-28,400cm⁻¹, preferably in the range of 28,374-28,375 cm⁻¹ or in the range of28396-28398 cm⁻¹, more preferably, 28,374.6 cm⁻¹, 28,396.3 cm⁻¹,28,397.1 cm⁻¹, or a combination thereof, and even more preferably,28,374.63 cm⁻¹, 28,396.32 cm⁻¹, 28,397.06 cm⁻¹, or a combinationthereof.

The photodissociating laser used for the photodissociating the vapormixture in the present disclosure may be an optic fiber laser with highenergy efficiency and simpler maintenance and management, but is notlimited thereto. The optic fiber laser contains an active medium insideoptic fibers, wherein the medium contains a low-level rare-earth halide.Such an optical fiber laser may be compact in size, light in weight, andconvenient in maintenance and management, and particularly, may havehigh energy efficiency and a broad lasing wavelength region.Accordingly, such an optical fiber laser can be adjusted in intensity(output) across a broad region, and can selectively generate wavenumbersfor photodissociation of formaldehyde, and thus may be suitable for usein the present disclosure.

The vapor mixture may be irradiated with a laser of such wavenumbers toselectively photodissociate ¹⁷O-containing formaldehyde. At aformaldehyde transition wavelength used for the photodissociationprocess, the absorption cross section of ¹⁷O -containing formaldehydemay be in the range of 3.0-3.5 10⁻¹⁹ cm²/molecule under a pressure ofseveral Torrs, for example, under 15 Torrs, and the backgroundabsorption cross section of the other isotopologues may be in the rangeof about 8*10⁻²¹ cm²/molecule, while the isotope selectivity for ¹⁷O maybe about 400.

In the present disclosure, the ¹⁷O-containing water may be heavy water,light water, or a mixture thereof.

In addition, following the obtaining a gas mixture containing hydrogenand ¹⁷O -enriched carbon monoxide, ¹⁷O -depleted water, and residualformaldehyde, isolating the residual formaldehyde by cooling andcondensing the ¹⁷O -depleted water and the residual formaldehyde, may befurther comprised.

Through the above process, formaldehyde undissociated by thephotodissociation process may be collected and discharged, and thephotodissociated products produced by photodissociation, hydrogen (H₂)and carbon monoxide (CO), may be isolated and collected. Here, theproducts produced by the photodissociation process, hydrogen and carbonmonoxide, and formaldehyde remaining undissociated through thephotodissociation process, may be cooled and condensed to be collected.The undissociated formaldehyde, having a freezing point of −92° C., maybe cooled below the freezing point to be condensed. Accordingly, it ispreferable that the cooling be carried out at a temperature less than orequal to 181 K (−92° C.) . For example, the cooling may be carried outat a temperature in the range of 100-181 K.

In particular, since hydrogen and carbon monoxide remain in a gaseousstate even under formaldehyde condensation conditions, thephotodissociation products, hydrogen and carbon monoxide, may becollected in the gaseous state and then isolated from the formaldehyde.

Since the formaldehyde discharged therefrom may comprise theformaldehyde undissociated during the photodissociation process andpossibly containing the oxygen isotope, such formaldehyde may berecirculated to be used in a formaldehyde photodissociation process.

Although as described above, the process for isolating an oxygen isotopefrom water may be used to collect the oxygen isotope, such a process maybe further used to isolate and remove radioactive isotopes. Accordingly,such a process may find suitable applications in the treatment ofradioactive carbon wastes.

In detail, the materials used as coolant and structural material ofnuclear reactors contain isotopes such as ¹⁷O, and these stable isotopesreact with reactor neutrons to form a radioactive isotope, ¹⁴C.Accordingly, if the amount of ¹⁷O contained in heavy water and the likeis reduced to 1/10 or less, it is possible to reduce ¹⁴C emissions fromheavy water reactors by 90% or more.

However, the carbon monoxide produced by the above-describedphotodissociation of formaldehyde may contain an isotope of oxygen, ¹⁷O.Accordingly, by performing a catalytic methanation reaction on thephotodissociated products containing such carbon monoxide and hydrogen,the isotope of oxygen may be recovered.

According to another aspect of the present disclosure, a process forobtaining ¹⁷O-enriched water may include an operation of obtaining a gasmixture containing hydrogen and ¹⁷O -enriched carbon monoxide, ¹⁷O-depleted water, and residual formaldehyde from ¹⁷O -containing water bythe process for isolating ¹⁷O from water of the present disclosure; anda catalytic methanation operation of adding hydrogen to the gas mixtureto induce a catalytic methanation reaction to synthesize methane (CH₄)and ¹⁷O -enriched water (H₂ ¹⁷O ) through methanation.

In detail, once hydrogen and carbon monoxide produced by thephotodissociation are isolated and collected, it is preferable that acatalytic methanation reaction 504 be carried out to isolate ¹⁷Otherefrom. Through such a catalytic methanation reaction, water (H₂O)and methane (CH₄) can be produced from the hydrogen and the carbonmonoxide 505, and by condensing and collecting the water thus obtained,¹⁷O -enriched water can be extracted as a final product.

In other words, by supplying hydrogen to the hydrogen and carbonmonoxide produced by the photodissociation, thereby giving rise to acatalytic methanation reaction, water and methane can be produced.

Catalysts that can be used in the catalytic methanation reaction are notlimited to any particular material, and may be any one commonly used inthe related art. Examples of such catalysts include Raney nickel.

Moreover, the ¹⁷O-enriched water (H₂ ¹⁷O ) obtained through methanationmay be recirculated and used as a starting material for the process forisolating an oxygen isotope from water, to carry out a ¹⁷O -enrichedwater production process in two stages. In this case, a product enrichedwith ¹⁷O isotope to 90% or higher may be obtained.

In other words, to isolate an oxygen isotope, water containing theoxygen isotope may be synthesized 505 through a catalytic methanationreaction from hydrogen and carbon monoxide produced by a firstphotodissociation process; and additional formaldehyde, not containingthe oxygen isotope, may be supplied to the water to induce oxygenisotope exchange reactions between the synthesized water andformaldehyde, to thereby produce formaldehyde containing the oxygenisotope.

Through such oxygen isotope exchange reactions, the oxygen isotopecontained in the water enriched through the photodissociation may betransferred to formaldehyde, and accordingly, formaldehyde containingthe oxygen isotope may be obtained. Further, the formaldehyde thusobtained, containing the oxygen isotope, may be supplied to a secondphotodissociation process to be photodissociated, thereby isolating theoxygen isotope therefrom.

Also, the oxygen isotope may be isolated by first producing methane andwater containing the oxygen isotope through a catalytic methanationreaction, and then condensing and collecting the water thus produced.

As described above, through two stages of the oxygen isotope isolationprocess, using the aforementioned process, the concentration factor ofthe oxygen isotope may be increased up to 30,000.

The process for isolating ¹⁷O from water according to the presentdisclosure has selectivity for ¹⁷O of 400, and can focus energy solelyon ¹⁷O whose abundance ranges from 0.037% to 0.059%, to isolate thesame, thus achieving extremely high energy efficiency, and may enablelarge-batch production in relatively small facilities.

Further, the present disclosure, when applied to the production of ¹⁷O-depleted heavy water to increase cost-effectiveness thereof, may serveto reduce ¹⁴C formation from heavy water reactors by 90% or more and todramatically reduce the production costs of ¹⁷O-enriched water, thusenabling various applications of ¹⁷O -enriched water.

Hereinbelow, the present disclosure will be described in greater detailthrough specific examples. The following examples are examples to assistin an understanding of the present disclosure and are not meant to berestrictive on the scope of the present disclosure.

EXAMPLES

1. Confirmation of Wavelengths for Formaldehyde Photodissociation Usefulfor ¹⁷O Isolation

Formaldehyde gas (H₂CO), when irradiated with 340-360 nm UV light, isphotodissociated into hydrogen molecules (H₂) and carbon monoxide (CO)as shown in Equation 1.H₂CO+hv→H₂+CO   Equation 1

FIG. 2 and FIG. 3 show the photodissociation spectra of formaldehyde, asmeasured at 343 K using a narrow-linewidth single mode laser having alinewidth of 60 MHz.

In FIG. 2 and FIGS. 3, 101 and 201 are spectra of formaldehydecontaining ¹⁷O in natural isotopic abundance of 0.037%, and 102 and 202are photodissociation spectra of formaldehyde containing ¹⁷O in isotopicabundance of 3.8%. Here, the aqueous formaldehyde solution used containsformaldehyde in a molar ratio of formaldehyde to water of 0.2, the totalvapor pressure of the aqueous solution is 15 Torr, and the pressurebroadening is about 500 MHz.

(a) shown in FIG. 2, and (b) and (c) shown in FIG. 3 arephotodissociation wavelengths useful for ¹⁷O isolation, whereinwavenumbers of the respective photodissociating lasers are 28,374.63cm⁻¹, 28,396.32 cm⁻¹, and 28,397.06 cm⁻¹, respectively. In (a) shown inFIG. 2, and (b) and (c) shown in FIG. 3, the absorption cross section of¹⁷O formaldehyde was 3.0-3.5×10⁻¹⁹ cm²/molecule, the backgroundabsorption cross section of the other isotopologues was about 8×10⁻²¹cm²/molecule, and the selectivity for ¹⁷O was about 400.

In particular, isotope selectivity S is defined by Equation 2 below,where C_(F) is a ¹⁷O isotopic abundance of the starting material, andC_(P) is a ¹⁷O isotopic abundance of the product.

$\begin{matrix}{S = \frac{C_{P}/( {1 - C_{P}} )}{C_{F}/( {1 - C_{F}} )}} & {{Equation}\mspace{14mu} 2}\end{matrix}$

2. Relationship Between the ¹⁷O Abundance in Photodissociated Productand the (¹⁷O) Abundance in Tail Water

FIG. 4 shows the relationship between the concentration of aphotodissociated product and a component ratio in tail water in anisolation process having selectivity for ¹⁷O of 400.

The graph 301 is the case of heavy water with an ¹⁷O abundance of0.059%, and the graph 302 is the case of light water with an ¹⁷Oabundance of 0.037%. In a process of removing ¹⁷O isotope from heavywater to 0.005%, the isotopic abundance of ¹⁷O in the photodissociatedproduct, carbon monoxide, becomes 11%. In a process of concentrating¹⁷O, using light water as a starting material, when the ¹⁷O isotopicabundance in tail water is 0.02%, an ¹⁷O product having enrichedisotopic abundance to 10% may be obtained, whereas if another isolationprocess is added to carry out the process in two stages, an ¹⁷O producthaving enriched isotopic abundance up to 90% or higher may be obtained.

Example 1 Isolation of Oxygen Isotope from Water

An aqueous formaldehyde solution 501 prepared by dissolving formaldehydein heavy water in a molar ratio of 0.2 or less to water was heated to343 K, and vapor of heavy water and formaldehyde generated thereby wasinjected into a photodissociation device 502 to a pressure about 5-15Torr. Inside the photodissociation device 502, being heated at 343 K,¹⁷O formaldehyde is photodissociated, and at the same time,oxygen-isotope exchange reactions such as that shown in Equation 3, takeplace between residual formaldehyde and heavy water.H₂C¹⁶O+D₂ ¹⁷O⇄H₂C¹⁷O+D₂ ¹⁶O   (3)

Although the oxygen-isotope exchange reactions occur within a fewminutes, hydrogen-deuterium exchange reactions are extremely slow,having a reaction time spanning a few hundred hours, and thus, during¹⁷O isolation processes, hydrogen isotopes are not exchanged.Accordingly, there is no loss of heavy water serving as the startingmaterial, in ¹⁷O removal processes.

In particular, the ¹⁷O -depleted heavy water (D₂O) in which ¹⁷O has beendepleted to 0.005% or less, is trapped in a water-trap device 503 andbecomes the final product. The residual formaldehyde is trapped in aliquid nitrogen-trap maintained at 100 K, and is thereby isolated fromsyngas (H₂+C¹⁷O), a photodissociated product. If necessary, the syngasmay be transferred to a methanation device 504 to which hydrogen isadditionally supplied, to produce ¹⁷O-enriched water enriched to about10% 505 as a byproduct.

Through the above-described processes, ¹⁷O contained in the heavy waterwas depleted to produce ¹⁷O -free heavy water (D₂O).

Example 2 Production of ¹⁷O -Enriched Water

An aqueous solution 501, prepared by dissolving formaldehyde in water ina molar ratio of about 0.1-0.2 was heated to 373-393 K, and vapor of theaqueous formaldehyde solution generated thereby was injected into aphotodissociation device 502 to a pressure of about 5 Torr. Inside thephotodissociation device 502 being heated at 373 K, ¹⁷O formaldehyde isphotodissociated, and at the same time, oxygen-isotope exchangereactions take place between formaldehyde and water.

Residual formaldehyde and water, remaining after the photodissociation,are trapped in a liquid-nitrogen trap maintained at 100 K and therebyisolated from syngas, which is a photodissociated product. The syngas istransferred to a methanation device 504 to which hydrogen isadditionally supplied, to be transformed into ¹⁷O -enriched waterenriched to about 10% 505.

A recirculation line 506 may be provided for a second stage process. Inthe second stage, an aqueous solution 501 prepared by dissolvingformaldehyde in 10% ¹⁷O -enriched water in a molar ratio of about0.1-0.2, may be used. The isolation process including two stages mayproduce ¹⁷O -enriched water enriched to 90% or higher.

Through the processes as set forth above, ¹⁷O -enriched water may beproduced using water as the starting material.

As set forth above, according to the examples, a process for isolating¹⁷O from water, having selectivity for ¹⁷O of 400, may focus energysolely on ¹⁷O with an abundance of 0.059%, to isolate the same, thusachieving extremely high energy efficiency, and may enable large-batchproduction in relatively small-scale facilities. Further, the presentdisclosure may be applied to the production of ¹⁷O -depleted heavy waterto increase the cost-effectiveness thereof, may reduce ¹⁴C formationfrom heavy water reactors by 90% or more, and may dramatically reducethe production cost of ¹⁷O -enriched water, thus enabling variousapplications of ¹⁷O -enriched water.

While exemplary embodiments have been shown and described above, it willbe apparent to those skilled in the art that modifications andvariations could be made without departing from the scope of the presentinvention, as defined by the appended claims.

What is claimed is:
 1. A process for isolating ¹⁷O from water,comprising: preparing an aqueous formaldehyde solution by mixing ¹⁷O-containing water with formaldehyde; preparing a vapor mixturecontaining water vapor and formaldehyde vapor by heating the aqueousformaldehyde solution; and obtaining ¹⁷O-depleted water, residualformaldehyde, and a gas mixture containing hydrogen and ¹⁷O -enrichedcarbon monoxide, through photodissociating the vapor mixture, wherein awavenumber of a photodissociating laser for the photodissociating thevapor mixture is in a range of 28,370-28,400 cm¹.
 2. The process forisolating ¹⁷O from water of claim 1, wherein the formaldehyde is mixedwith water in a molar ratio of formaldehyde to water in a range of0.01-0.3.
 3. The process for isolating ¹⁷O from water of claim 1,wherein the heating is carried out at a temperature in a range of320-400 K.
 4. The process for isolating ¹⁷O from water of claim 1,wherein the photodissociating the vapor mixture is carried out under apressure in a range of 1-15 Torr.
 5. The process for isolating ¹⁷O fromwater of claim 1, the wavenumber of a photodissociating laser for thephotodissociating the vapor mixture is 28,374.63 cm⁻¹, 28,396.32 cm⁻¹,28,397.06 cm⁻¹, or a combination thereof.
 6. The process for isolating¹⁷O from water of claim 1, wherein the photodissociating laser used forthe photodissociating the vapor mixture is an optic fiber laser.
 7. Theprocess for isolating ¹⁷O from water of claim 1, wherein the ¹⁷O-containing water is heavy water, light water, or a mixture thereof. 8.The process for isolating ¹⁷O from water of claim 1, further comprising,following the obtaining, ¹⁷O -depleted water, residual formaldehyde, anda gas mixture containing hydrogen and ¹⁷O -enriched carbon monoxide,cooling and condensing them separate O-depleted water and the residualformaldehyde from the gas mixture containing hydrogen and ¹⁷O-enrichedcarbon monoxide.
 9. The process for isolating ¹⁷O from water of claim 8,wherein the cooling is carried out at a temperature less than or equalto 181 K (−92° C.).
 10. A process for producing ¹⁷O-enriched water,comprising: an operation of obtaining ¹⁷O-depleted water, residualformaldehyde, and a gas mixture containing ¹⁷O-enriched carbon monoxideand hydrogen, from ¹⁷O -containing water by the process for isolating¹⁷O from water of claim 1; and a catalytic methanation operation ofadding hydrogen to the gas mixture to induce a catalytic methanationreaction to synthesize methane (CH₄) and ¹⁷O -enriched water (H₂ ¹⁷O )through methanation.
 11. The process for producing ¹⁷O -enriched waterof claim 10, wherein the ¹⁷O -enriched water (H₂ ¹⁷O ) obtained throughmethanation is recirculated as a starting material for the process forisolating ¹⁷O from water, to carry out a ¹⁷O -enriched water productionprocess in two stages.